test(bin-e2e): dlopen the shipped js plugin cdylib for real

[raphaelvigee]

Part 8/8 of the stack — closes a gap flagged repeatedly since M0: plugin-js-cdylib was lint/fmt covered (devenv.nix's qualityCrates) but never actually loaded across the real ABI seam by any test.

What's here

• devenv.nix's e2e script now stages plugin-js-cdylib as a fourth artifact, symmetric with go/gha in both the local-build and HEPH_E2E_FROM/CI branches (fingerprinting, copying, macOS-portable-patching all updated together).
• Four new real bin-e2e tests in crates/bin-e2e/tests/plugin_dylib_js.rs:
  • shipped_js_cdylib_loads_and_answers_across_the_abi — construction + the sync inspect functions ABI call round-trips cleanly.
  • shipped_js_cdylib_discovers_a_real_workspace_package — query -e //... against a real pnpm-shaped fixture resolves //packages/foo:package_info.
  • shipped_js_cdylib_resolves_pnpm_workspace_glob_membership — proves a package outside the packages/* glob is never admitted as a workspace member, across the real seam.
  • js_plugin_construction_failure_logs_before_the_abort — the same log-sink-before-abort regression coverage the go test already has.

Two things review caught worth naming

The first draft of shipped_js_cdylib_loads_and_answers_across_the_abi asserted inspect functions produced completely empty stdout — wrong, and it failed deterministically: the fs builtin provider's own functions are always registered regardless of plugin config, so stdout is never actually empty. Fixed to assert no line starts with js. instead (the js Provider never overrides functions(), unlike go's build_addr).

The discovery test's own doc comments originally claimed to exercise pnpm's workspace-glob membership resolution — they didn't. Traced it: Provider::list/list_packages discover packages by package.json presence alone, independent of pnpm-workspace.yaml content entirely; the glob-resolution path (workspace.rs's resolve_members) is only reached from Provider::get, which a plain query -e //... never calls. Rather than leave an overclaiming comment standing, added the dedicated shipped_js_cdylib_resolves_pnpm_workspace_glob_membership test that actually reaches that path, and corrected the original test's docs.

Verified for real, not just compiled

Ran the full e2e devenv script end to end — release build of heph + all three plugin cdylibs, staged, macOS-portable-patched, full bin-e2e suite against real dlopen'd artifacts:

tests/cli.rs:            4 passed
tests/plugin_dylib.rs:    4 passed
tests/plugin_dylib_js.rs: 4 passed  (all new)
tests/shell_pty.rs:       3 passed
tests/tui_pty.rs:         2 passed
17/17 total

Test plan

• cargo build -p bin-e2e --tests
• cargo clippy -p bin-e2e --all-targets -- -D warnings (clean)
• cargo fmt --check -p bin-e2e
• nix-instantiate --parse devenv.nix
• Full e2e run against real staged release artifacts — 17/17 passed
• CI (tst, lint, bin_e2e) on this PR

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